Antenna structure



March 21, 1950 B RN 2,501,020

' ANTENNA STRUCTURE Filed Nov. 6, 1945 INVENTOR ROBE/P T B. BARNES A T TORNEV Patented Mar. 21, 1950 etuutl auntie ANTENNA STRUCTURE Robert B. Barnes. Cambridge, Mass, assignor to the United States of America as represented by the Secretary of War Application November 6, 1945, Serial No. 627,049

2 Claims" (Cl. 250-33) This invention relates to antennas for transmission and reception of electrical energy at radio frequencies. More particularly it relates to means for supporting conical antennas to aircraft or other structures which adapt the antennas to operation over a wider range of frequencies than has been possible heretofore.

It has been the common practice of the prior art to have the coaxial transmission line which feeds electrical energy to a conical antenna serve also as a mechanical support for the antenna. This has been accomplished by filling the space between the inner and outer conductors of the transmission line at the apex of the cone with a solid dielectric material to lend rigidity and mechanical support to the antenna structure. Such a support requires that the antenna be fastened to the nacelle which shrouds it and which is attached to the fuselage of the aircraft or other structure because the single transmission line support at the bottom is not strong enough to securely position the antenna.

It is an object of the present invention to provide a conical antenna and support which operates over a wider frequency range than similar antennas in the prior art.

It is also an object of the present invention to provide a support for a conical antenna which is made of dielectric material and securely attached to the side or top of the antenna and which permits elimination of the use of dielectric material in the tapered section of the coaxial transmission line which conveys electrical energy to or from the antenna.

It is a further object of the present invention to provide a mechanical support for a conical antenna which is made of dielectric material and which is external to the conical antenna and not associated with the transmission line which conveys electrical energy to or from the antenna.

Generally, this invention comprises the aflixing of a ring of dielectric material to the sides of a conical antenna and supporting that ring by a cylindrical dielectric support attached to the dielectric ring and enclosed by a protective nacelle made of dielectric material. This permits elimination of the dielectric supporting material in the tapered section of the coaxial transmission line connected to the antenna. The antenna may alternately be supported by a single skirt or a series of skirts made of insulating material attached to the sides or top of the conical antenna. This arrangement sacrifices none of the advantages of the dielectric ring and supporting cylinder.

Other objects, features, and advantages of this invention will suggest themselves to those skilled in the art and will become apparent from the following description of the invention taken in connection with the accompanying drawings in which:

Fig. 1 is a cross-sectional view of a conical antenna with a supporting structure constructed in accordance with the present invention; and

Fig. 2 is a diagrammatic sketch showing another embodiment of a supporting structure, in accordance with the present invention.

Referring more particularly to Fig. 1, the conical antenna and its associated structure are generally designated by Ill. The configuration of structure l0 may be more fully appreciated by visualizing it as a figure of revolution about axis AA. The tapered coaxial section II is connected to a coaxial transmission line by connector l2 and electrical energy is conveyed to or from the conical antenna l3 through its apex M. The tapered section I l is constructed so that its characteristic impedance at its juncture with connector I2 is equal to the characteristic impedance of the transmission line used and its characteristic impedance at juncture I 4 with the antenna I3 is equal to the radiation resistance of antenna l3. This is to insure minimum electrical discontinuity and loss of energy by the coaxial connections to the transmission line at l2 and to the antenna [3. The inner conductor l5 of tapered section H is secured to the apex M of the conical antenna I 3 by the screw connector IS. The washer IBA is used to position and adjust the position of antenna I3 and inner conductor l5 to the correct length for mechanical snugness. The number of such washers used varies in accordance with their thickness. The outer conductor ll of tapered section II is secured to the antenna supporting structure l8, often the fuselage of an aircraft, by the structure l9 which is constructed to position antenna I3 above any metallic parts of the structure such as screws 2|, 2|. This prevents distortion of the antenna radiation pattern.

The nacelle 20 made of dielectric material, completely surrounds the conical antenna l3 and is attached to the supporting structure l8 such as the wall of an aircraft fuselage by means of screw connectors 2|, 2|. The conical antenna I3 is fastened to the nacelle 20 at its top by screws 22 and 23.

The metallic ring 24 fits around the side of antenna l3. Dielectric disc 25 fits around ring 24 as shown at 2B and rests upon the cylindrical dielectric support 21. The dielectric support 21 is supported by the supporting structure l8 and snugly fits inside the nacelle 20.

Referring to Fig. 2, the conical antenna 13, is held in position by mechanical support 30 which is secured to the supporting structure iii. A single dielectric supporting skirt or series of dielectric supporting skirts 3| are attached to the ring 24 at one end and to the structure l8 at their other end thereby giving rigid and permanent support to antenna l3. Supporting skirts 3| may be attached directly to antenna IS without the use of ring 24.

It has been found that in the use of antennas of this type where sectionsof solid dielectric material have been used in tapered section II, the efficient range of operating frequencies has been limited by the electrical discontinuities introduced by the dielectricmaterial. The elimination of the dielectric supporting material in ta pered section I l and the use of a supporting structure embodying the principles of this invention has allowed operation of this type of antenna over a much wider frequency range than any antenna of the prior art.

While there has been shown two particular embodiments of the supporting structure of this invention, it is readily seen that the principles of this invention embrace all methods of mechanically supporting within its nacelle a conical antenna at its top or its side.

While there has been here described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention.

What is claimed is:

1. An antenna system comprising a conical antenna, means for supporting said antenna relative to a mounting surface, said means comprising a dielectric ring disposed about the outside surface of said antenna. between its base and apex, said ring being narrow relative to the length of said antenna, a dielectric disc-like member attached at its inner periphery to said dielectric ring and supported on said mounting surface by a tubular dielectric structure fixed to the outer periphery of said disc-like member, a dielectric nacelle enclosing said aforementioned elements, means to fix said tubular dielectric structure and said nacelle to said mounting surface, means to fix the base of said antenna to the top of said nacelle, and adjustable means to a conductor within the apex of said antenna, said last named means including an axial channel formed in the apex of said antenna and complementary in diameter to said conductor.

2. The device according to claim 1, wherein said conductor is provided with a shoulder and comprises the inner conductor of a coaxial line, the outer conductor of which is fixed to said mounting surface, and wherein said adjustable means further includes a plurality of spacing washers removably positioned about said inner conductor between said shoulder and said apex whereby the depth of penetration of said inner conductor into said channel may be regulated.

ROBERT B. BARNES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Datc 2,175,252 Carter Oct. 10, 1930 2,175,254 Carter Oct. 10, 1939 2,354,314 Harsted July 25, 1944.- 2,401,601 Atwood June 4, 1946 2,433,698 Hurst Dec. 30, 1947 FOREIGN PATENTS Number Country Date 114,368 Australia Dec. 24, 1941 

